The present invention pertains to foam pads for buffing and, more particularly, to rotary foam pads for buffing and polishing painted or similarly finished surfaces.
Foam buffing pads are now used in many buffing and polishing operations where synthetic or natural fiber pads, such as tufted wool pads, had previously been used. In particular, open cell polyurethane foam pads, with both reticulated and non-reticulated cell structures, have become particularly popular. However, despite the actual advantages of polymer foam pads over fibrous and tufted pads, there are still a number of inherent disadvantages attendant the use of foam pads. These disadvantages include xe2x80x9cchatterxe2x80x9d or jumping of the pad by excess frictional surface contact between flat working surface portions of the pad and the surface of the work being finished; splattering of the polish or other finishing compound as a result of the compound being thrown radially outwardly by centrifugal force; and, burning of the surface of the work being finished by the high speed outer edge portions of the rotary pad.
Attempts have been made to minimize or eliminate these problems by varying the type and density of foam used and by changing the working surface of the pads. Initially, foam pads were made of a generally cylindrical disc with a flat planar working face and, typically, with a radiused outer edge providing the transition between the working face and the outer cylindrical edge face. However, flat pads are particularly subject to chatter and provide little deterrent to the splatter of polish. Flat faced pads also give the operator little control over variations in the working surface actually in contact with the work surface being finished or polished. One attempt at solving the problems presented by flat foam buffing pads was the introduction of buffing pads having working surfaces with a convoluted or waffle shape. One such pad was previously made by Lake Country Manufacturing, Inc. Although this pad provided variable working surface contact by varying operator-applied pressure, surface contact was somewhat difficult to control and the pad did little to prevent splatter. A different approach to solving the prior art problems is shown in U.S. Pat. No. 5,527,215 where a cylindrical foam pad has a recessed center portion or portions within which the polishing compound may be trapped against radial splatter. This pad also provides the ability to alter the working surface contact by varying operator-applied pressure. However, neither of the foregoing pads adequately solves all of the prior art problems and, in addition, neither provides an operator with the ability to create true graduated surface contact which is uniform and predictable. Finally, rotary buffing pads are often inherently unbalanced because of the manner in which the pads are finished or mounted, resulting in undesirable vibrations, added chatter, and operator fatigue.
In accordance with the present invention, a rotary foam buffing pad and the manner in which it is manufactured provide a unique solution to all of the foregoing problems with prior art foam buffing pads. The result is a pad with superior performance in the elimination of chatter, prevention of polish splatter, and operator control of the working surface contact area.
In its preferred embodiment, the rotary compressible foam buffing pad of the present invention has a working face comprising a concave central contact surface and a peripheral outer contact surface. The outer contact surface provides an area of continuous working contact and encloses the central contact surface, precluding any substantial working contact by the central contact surface when the pad is generally uncompressed, but providing increased radial inward expansion of the area of working contact with increasing pad compression. The concave central contact surface extends radially inwardly from the outer contact surface to a central area of maximum concavity. The buffing pad includes a mounting face opposite the contact surface and an annular edge face which extends between and joins the mounting face and the outer contact surface.
The outer peripheral first contact surface preferably comprises a planar annular band. The inner concave contact surface may be conical or spherical. The pad may include a central opening which extends through the pad body on its rotational axis. Further, the annular edge face of the pad which joins the working face and the mounting face may be generally cylindrical or frustoconical and, in the latter case, having a maximum diameter where it joins the working face. The mounting face of the pad adapts the same for attachment to a backing plate, either with a permanent connection or with a demountable fastener, such as a hook and loop type fastening system.
In accordance with a preferred method for making a rotary foam buffing pad of the present invention, a generally cylindrical preform of foam material is utilized, which preform has generally flat parallel front and rear faces which are interconnected by a cylindrical edge face, the method comprising the steps of: rotating the preform on its axis, and dynamically forming a concave working face on the front face during rotation. The method may also include the step of dynamically forming a conical surface on the edge face during rotation. The preform is preferably rotted by supporting the same by its rear face on the backing plate, and grinding the front face of the pad while it is being rotated to move material from the face to provide the concave working face. The grinding step preferably includes texturizing the working face to enhance buffing performance. The edge face may also be ground and texturized in a similar manner.